The present invention relates to a method for preparing golf balls with surface indicia having metallic luster. The invention also relates to golf balls obtained by such a method.
Golf balls are commonly marked by directly or indirectly printing indicia, including letters, numbers, trade names and images such as logos on the surface of the ball. Brightness is sometimes imparted to these marks to give the ball a more vivid and aesthetically pleasing appearance. A technique for imparting brightness that has been described involves preparing an ink that contains a metal powder such as aluminum or copper powder, and using the ink to apply metallic marks to a golf ball.
Marking methods for obtaining attractive images having a metallic luster include printing methods that use a transfer film. For example, JP-A 8-47551 discloses a production process which involves producing a transfer film having the following layer construction: plastic base film/release layer/surface protecting layer/metal thin-film layer/thermoplastic resin layer, bringing the thermoplastic resin layer side of the transfer film into contact with the surface of the golf ball and applying heat and pressure, then peeling off the plastic base film/release layer so as to transfer to the golf ball surface the thermoplastic resin layer/metal thin-film layer/surface protecting layer. However, a drawback of this method is that production of the transfer film involves a complicated set of operations. First, an intermediate film having the following layer construction is formed: release layer/surface protecting layer/water-soluble resin layer (formed in areas where the metal thin-film is not formed)/metal thin-film layer. Next, the water-soluble resin layer is removed by rinsing the intermediate film with water, thereby obtaining a metal thin-film layer having the intended lettering and images. The thermoplastic resin is then coated on top of the thin-film layer to complete production. This complexity results in a high cost per mark applied to the golf ball.
To simplify the production of transfer film obtained by such a complicated set of operations, JP-A 2000-1692 discloses a method of producing transfer film which involves forming a surface protecting layer and an ink layer on a plastic substrate, pressure bonding a metal thin-film over the entire surface thereon so as to form a metal thin-film layer which, when peeled off, will remain only over the ink layer due to the tackiness of the ink, then forming over the metal thin-film layer an adhesive layer. Unfortunately, in this method, depending on the stability of tack by the ink layer and the pressure bonding conditions, adhesion between the ink layer and the metal thin-film layer is sometimes greater than adhesion between the plastic substrate and the surface protecting layer or adhesion between the surface protecting layer and the ink layer. In such cases, peeling occurs at the plastic substrate and the surface protecting layer or at the surface protecting layer and the ink layer, making it impossible to efficiently obtain a transfer film bearing the intended lettering and graphics.